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Fu-sheng compressor

I have a mammoth unit and the 1st stage compressor constantly loads. On start up, it loads immediately with the load solenoid energized(valve closed). When the control energizes the unload solenoid, the compressor unloads and then immediately loads when the unload solenoid de-energizes. I replaced the load solenoid as the probable culprit and fired the compressor back up. The compressor would not load at all for about 1 hour and then started loading without de-energizing the load solenoid. My next step is to valve off the capillary line that feeds the load solenoid, but I have some time until that can be done...Soooooooo--I wanted to poll the gallery and ask your expert opinions since this is the first Fu-sheng I have worked on. Does this sound like an internal lip-seal type problem and if so, has anyone cracked open one of these compressors?

Mammoth units are commonly found to be wired wrong as far as the load/unload solenoids, especially on the larger units say 150 tons and up. Check your wiring first. DO NOT assume it is right until you actuall check it. Is the unit starting with the compressor fully loaded?

Mammoth units are commonly found to be wired wrong as far as the load/unload solenoids, especially on the larger units say 150 tons and up. Check your wiring first. DO NOT assume it is right until you actuall check it. Is the unit starting with the compressor fully loaded?

This is where I was going, James. I rarely make dogmatic statements, and different folks do things different ways, but as a rule, you energize to load/unload. Sounds like you have something crossed up, or you have the wrong valve.

And VTP - you need to look at where I'm from. I ain't ever said one thing really fast!!!

This is a 160 hp machine so I have 2 other compressors to compare operation sequences. I have also manually energized and de energized the solenoids to try to get it to do what it is supposed to. The load solenoid (SV2) is a normally open valve that closes when energized, so it only deenergizes to load. This valve admits high pressure oil to move the slide to load pushing against spring pressure. The unload solenoid (SV1) is internally tee'd into the oil passage that feeds the slide valve and releases oil pressure when the solenoid valve is energized thus unloading the compressor. I found a rudimentary diagram of the operation sequence and internal design, but I have never heard of them much less opened one up. This compressor is a 25-100% modulating machine.

The compressor does not appear to be starting loaded, but it is fully loaded within 5 seconds of starting with the load solenoid hardwired energized(closed). I am making this call based on observing the amp draw on start.

James
From what you have explained and from working with several of the screw mfg's it sounds like you have a bad slipper seal in the slide valve pistion. Good luck with were you go from here. You do not know untill you get the oil seperator off and the discharge cover plate if you have tired iron. If the slide valve piston chamber is egg shaped it is tired iron
Robert 1078